Electric linear actuators are driven by either an AC or DC motor. This article will highlight the main differences between these two motor types in order to assist you in the selection of the correct linear actuator motor.
AC and DC motors run on the same principle. Alternating magnetic fields caused by alternating current direction cause a shaft to rotate. The differences between these two current types determine the motor characteristics.
DC stands for Direct Current while AC stands for Alternating Current. DC has current that runs continually in a single direction. This is often seen in batteries and fuel cells. AC has a current that reverses direction at a certain number of times per second. US households are powered by AC which reverses 60 times per second, or more commonly referred to as “60 hertz”.
AC is typically the choice for high power applications such as in large factories because it is easier to convert from higher to lower voltages. It also has fewer electrical losses when sent over long distances which is why it is used on household power lines.
For lower power applications, you will find a mixture of AC and DC motors. For example, in our homes where the power source is primarily AC, you will find fans, washing machines, and wired power tools with AC motors. For most mobile applications such as cars or cordless devices, DC is much more common since these applications are powered with a battery which is a DC power source.
There are ways to convert between AC and DC power. In Tesla Motors’ electric cars you will find a DC battery that goes through an inverter to power AC motors. In our homes, you have AC from the wall socket which gets turned into DC using a converter (an example of which is our PA-20 control box which combines a converter with bidirectional controls in a simple package). This is very common with automated furniture that uses electric linear actuators such as reclining chairs, hospital beds, and standing desks.
As mentioned earlier, both AC and DC motors have alternating magnetic fields caused by alternating current direction.
DC motors have a brush and commutator on the rotor that physically alters the path of electricity to reverse the current direction. Since AC motors have naturally alternating current, there is no need for this physical commutator. The brushes and commutator on DC motors increase the maintenance, often limit the speed and reduce life expectancy compared to AC motors.
Note that there is an exception to this, the brushless DC motor. As the name implies, it does not use physical brushes. It solves many of the faults with brushed DC motors but it does come with a higher cost and requires external controllers.
The speed of the DC motor is proportional to the amount of current through the coils. This means that the DC motor’s speed can be altered using a variety of techniques, the simplest being voltage regulation which can be achieved with a simple resistor or a voltage regulator device such as our AC-14 Speed Controller.
On the other hand, AC motors require the frequency of power input to change. AC motors need what is called a Variable Frequency Drive which will alter the incoming AC frequency. For simple applications, this is often quite expensive compared to the simpler solutions available for DC motors.
Final WordOn top of the three differences listed, you have certain factors such as torque control, heat production and many more. All of which are valuable factors that will determine the best electric linear actuator for an application.
Progressive Automations manufactures and distributes DC electric linear actuators. We serve a wide range of industries from medical to robotics. If you have any questions regarding our product and how it will suit your application, please feel free to call us and our knowledgeable engineers will assist you.